This invention relates generally to apparatus and method for controlling amount of fuel injected into engine cylinders by means of an injection pump or the like.
The amount of fuel injected into a multi-cylinder internal combustion engine has been conventionally controlled uniformly throughout all the cylinders in both gasoline engines and diesel engines. Namely, according to known electronic fuel injecting systems for gasoline engines, the valve-opening duration of electromagnetic valves respectively provided to individual cylinders is controlled such that the valve opening duration is common to all the cylinders, while according to known electronically controlled diesel engines, which have been recently put in practical application stage, the position of an injection amount-controlling member, such as a control rack or a spill ring, is controlled where the controlling member is common to all the cylinders.
Although such a control effected uniformly throughout all the cylinders of an engine is simple, there arises a problem of variation or scattering in injecting fuel amount throughout the cylinders. Therefore, in conventional apparatus high manufacturing precision is required when manufacturing various parts, such as injection valves, injection conduits or the like, used in the injection system to reduce such variation throughout the cylinders. Such high manufacturing precision or accuracy necessarily increases the manufacturing cost. Furthermore, even though the precision of used parts have been increased to its limit so that variation throughout cylinders is minimized, the amount of fuel actually injected into engine cylinders has a chance to suffer from variation or scatter throughout cylinders due to secular change or external disturbance, such as a variation in actuating timing of intake and/or exhaust valves or the like.
Such variation in amount of fuel injected into cylinders of an engine results in irregular rotation of the engine crankshaft. Especially, during idling such irregular rotation is uncomfortable and noisy. Generally speaking, the engine rotational speed during idling is set to a low value in view of suppression of fuel cost. On the other hand, it is desired, especially for passenger automobiles, that engine rotation during idling is as smooth as possible thereby providing comfortable environment. Particularly, the above-mentioned irregular rotation during idling is desired to be reduced to achieve stable engine rotation.